#!/usr/bin/env perl

use strict;
use warnings;
use constant {
    NO_CASE => 0,
    COUNT => 1,
};

my (@data_all, %data_info);

while (<DATA>) {
    chomp;
    push @data_all, $_;

    if (exists $data_info{$_}) {
        ++$data_info{$_}[COUNT];
    }
    else {
        $data_info{$_} = [lc, 1];
    }
}

print "Sort alphabetically - ignore case\n";
print "$_\n" for
    map { $_->[0] }
    sort {
        $a->[1] cmp $b->[1]
    }
    map { [
        $_,
        $data_info{$_}[NO_CASE]
    ] }
    @data_all;

print "Sort alphabetically - capitalisation matters\n";
print "$_\n" for
    map { $_->[0] }
    sort {
        $a->[1] cmp $b->[1]
        ||
        $a->[2] cmp $b->[2]
        ||
        $a->[0] cmp $b->[0]
    }
    map { [
        $_,
        substr($data_info{$_}[NO_CASE], 0, 1),
        substr($_, 0, 1)
    ] }
    @data_all;

print "Sort by frequency - ignore alphabetical order\n";
print "$_->[1]: $_->[0]\n" for
    sort {
        $b->[1] <=> $a->[1]
    }
    map { [
        $_,
        $data_info{$_}[COUNT]
    ] }
    keys %data_info;

print "Sort by frequency - then by alphabetical order\n";
print "$_->[1]: $_->[0]\n" for
    sort {
        $b->[1] <=> $a->[1]
        ||
        $a->[0] cmp $b->[0]
    }
    map { [
        $_,
        $data_info{$_}[COUNT]
    ] }
    keys %data_info;

__DATA__
bb
Aa
CC
dD
bb
AA
dD
aa
BB
aa
dD
aA